Insights on the Structure, Molecular Weight and Activity of an Antibacterial Protein–Polymer Hybrid

다국어 초록 (Multilingual Abstract)

Protein–polymer conjugates are attractive biomaterials which combine the functions of both proteins and polymers. The bioactivity of these hybrid materials, however, is often reduced upon conjugation. It is important to determine and monitor the protein structure and active site availability in order to optimize the polymer composition, attachment point, and abundance. The challenges in probing these insights are the large size and high complexity in the conjugates. Herein, we overcome the challenges by combining electron paramagnetic resonance (EPR) spectroscopy and atomic force microscopy (AFM) and characterize the structure of antibacterial hybrids formed by polyethylene glycol (PEG) and an antibacterial protein. We discovered that the primary reasons for activity loss were PEG blocking the substrate access pathway and/or altering protein surface charges. Our data indicated that the polymers tended to stay away from the protein surface and form a coiled conformation. The structural insights are meaningful for and applicable to the rational design of future hybrids.
Stumbling block: Structural insights into the activity loss in an antibacterial PEGylated protein were revealed with EPR and AFM. The results indicate that PEG blocking the substrate access pathway and/or altering protein surface charges were the primary causes of the loss. The findings are meaningful for and applicable to the rational design of future hybrids.